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bb44e5d1
IM
1/*
2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
3 * policies)
4 */
5
4fd29176 6#ifdef CONFIG_SMP
84de4274 7
637f5085 8static inline int rt_overloaded(struct rq *rq)
4fd29176 9{
637f5085 10 return atomic_read(&rq->rd->rto_count);
4fd29176 11}
84de4274 12
4fd29176
SR
13static inline void rt_set_overload(struct rq *rq)
14{
637f5085 15 cpu_set(rq->cpu, rq->rd->rto_mask);
4fd29176
SR
16 /*
17 * Make sure the mask is visible before we set
18 * the overload count. That is checked to determine
19 * if we should look at the mask. It would be a shame
20 * if we looked at the mask, but the mask was not
21 * updated yet.
22 */
23 wmb();
637f5085 24 atomic_inc(&rq->rd->rto_count);
4fd29176 25}
84de4274 26
4fd29176
SR
27static inline void rt_clear_overload(struct rq *rq)
28{
29 /* the order here really doesn't matter */
637f5085
GH
30 atomic_dec(&rq->rd->rto_count);
31 cpu_clear(rq->cpu, rq->rd->rto_mask);
4fd29176 32}
73fe6aae
GH
33
34static void update_rt_migration(struct rq *rq)
35{
637f5085 36 if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
cdc8eb98
GH
37 if (!rq->rt.overloaded) {
38 rt_set_overload(rq);
39 rq->rt.overloaded = 1;
40 }
41 } else if (rq->rt.overloaded) {
73fe6aae 42 rt_clear_overload(rq);
637f5085
GH
43 rq->rt.overloaded = 0;
44 }
73fe6aae 45}
4fd29176
SR
46#endif /* CONFIG_SMP */
47
bb44e5d1
IM
48/*
49 * Update the current task's runtime statistics. Skip current tasks that
50 * are not in our scheduling class.
51 */
a9957449 52static void update_curr_rt(struct rq *rq)
bb44e5d1
IM
53{
54 struct task_struct *curr = rq->curr;
55 u64 delta_exec;
56
57 if (!task_has_rt_policy(curr))
58 return;
59
d281918d 60 delta_exec = rq->clock - curr->se.exec_start;
bb44e5d1
IM
61 if (unlikely((s64)delta_exec < 0))
62 delta_exec = 0;
6cfb0d5d
IM
63
64 schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
bb44e5d1
IM
65
66 curr->se.sum_exec_runtime += delta_exec;
d281918d 67 curr->se.exec_start = rq->clock;
d842de87 68 cpuacct_charge(curr, delta_exec);
bb44e5d1
IM
69}
70
63489e45
SR
71static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
72{
73 WARN_ON(!rt_task(p));
74 rq->rt.rt_nr_running++;
764a9d6f
SR
75#ifdef CONFIG_SMP
76 if (p->prio < rq->rt.highest_prio)
77 rq->rt.highest_prio = p->prio;
73fe6aae
GH
78 if (p->nr_cpus_allowed > 1)
79 rq->rt.rt_nr_migratory++;
80
81 update_rt_migration(rq);
764a9d6f 82#endif /* CONFIG_SMP */
63489e45
SR
83}
84
85static inline void dec_rt_tasks(struct task_struct *p, struct rq *rq)
86{
87 WARN_ON(!rt_task(p));
88 WARN_ON(!rq->rt.rt_nr_running);
89 rq->rt.rt_nr_running--;
764a9d6f
SR
90#ifdef CONFIG_SMP
91 if (rq->rt.rt_nr_running) {
92 struct rt_prio_array *array;
93
94 WARN_ON(p->prio < rq->rt.highest_prio);
95 if (p->prio == rq->rt.highest_prio) {
96 /* recalculate */
97 array = &rq->rt.active;
98 rq->rt.highest_prio =
99 sched_find_first_bit(array->bitmap);
100 } /* otherwise leave rq->highest prio alone */
101 } else
102 rq->rt.highest_prio = MAX_RT_PRIO;
73fe6aae
GH
103 if (p->nr_cpus_allowed > 1)
104 rq->rt.rt_nr_migratory--;
105
106 update_rt_migration(rq);
764a9d6f 107#endif /* CONFIG_SMP */
63489e45
SR
108}
109
fd390f6a 110static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
bb44e5d1
IM
111{
112 struct rt_prio_array *array = &rq->rt.active;
113
114 list_add_tail(&p->run_list, array->queue + p->prio);
115 __set_bit(p->prio, array->bitmap);
58e2d4ca 116 inc_cpu_load(rq, p->se.load.weight);
63489e45
SR
117
118 inc_rt_tasks(p, rq);
bb44e5d1
IM
119}
120
121/*
122 * Adding/removing a task to/from a priority array:
123 */
f02231e5 124static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
bb44e5d1
IM
125{
126 struct rt_prio_array *array = &rq->rt.active;
127
f1e14ef6 128 update_curr_rt(rq);
bb44e5d1
IM
129
130 list_del(&p->run_list);
131 if (list_empty(array->queue + p->prio))
132 __clear_bit(p->prio, array->bitmap);
58e2d4ca 133 dec_cpu_load(rq, p->se.load.weight);
63489e45
SR
134
135 dec_rt_tasks(p, rq);
bb44e5d1
IM
136}
137
138/*
139 * Put task to the end of the run list without the overhead of dequeue
140 * followed by enqueue.
141 */
142static void requeue_task_rt(struct rq *rq, struct task_struct *p)
143{
144 struct rt_prio_array *array = &rq->rt.active;
145
146 list_move_tail(&p->run_list, array->queue + p->prio);
147}
148
149static void
4530d7ab 150yield_task_rt(struct rq *rq)
bb44e5d1 151{
4530d7ab 152 requeue_task_rt(rq, rq->curr);
bb44e5d1
IM
153}
154
e7693a36 155#ifdef CONFIG_SMP
318e0893
GH
156static int find_lowest_rq(struct task_struct *task);
157
e7693a36
GH
158static int select_task_rq_rt(struct task_struct *p, int sync)
159{
318e0893
GH
160 struct rq *rq = task_rq(p);
161
162 /*
e1f47d89
SR
163 * If the current task is an RT task, then
164 * try to see if we can wake this RT task up on another
165 * runqueue. Otherwise simply start this RT task
166 * on its current runqueue.
167 *
168 * We want to avoid overloading runqueues. Even if
169 * the RT task is of higher priority than the current RT task.
170 * RT tasks behave differently than other tasks. If
171 * one gets preempted, we try to push it off to another queue.
172 * So trying to keep a preempting RT task on the same
173 * cache hot CPU will force the running RT task to
174 * a cold CPU. So we waste all the cache for the lower
175 * RT task in hopes of saving some of a RT task
176 * that is just being woken and probably will have
177 * cold cache anyway.
318e0893 178 */
17b3279b
GH
179 if (unlikely(rt_task(rq->curr)) &&
180 (p->nr_cpus_allowed > 1)) {
318e0893
GH
181 int cpu = find_lowest_rq(p);
182
183 return (cpu == -1) ? task_cpu(p) : cpu;
184 }
185
186 /*
187 * Otherwise, just let it ride on the affined RQ and the
188 * post-schedule router will push the preempted task away
189 */
e7693a36
GH
190 return task_cpu(p);
191}
192#endif /* CONFIG_SMP */
193
bb44e5d1
IM
194/*
195 * Preempt the current task with a newly woken task if needed:
196 */
197static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
198{
199 if (p->prio < rq->curr->prio)
200 resched_task(rq->curr);
201}
202
fb8d4724 203static struct task_struct *pick_next_task_rt(struct rq *rq)
bb44e5d1
IM
204{
205 struct rt_prio_array *array = &rq->rt.active;
206 struct task_struct *next;
207 struct list_head *queue;
208 int idx;
209
210 idx = sched_find_first_bit(array->bitmap);
211 if (idx >= MAX_RT_PRIO)
212 return NULL;
213
214 queue = array->queue + idx;
215 next = list_entry(queue->next, struct task_struct, run_list);
216
d281918d 217 next->se.exec_start = rq->clock;
bb44e5d1
IM
218
219 return next;
220}
221
31ee529c 222static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
bb44e5d1 223{
f1e14ef6 224 update_curr_rt(rq);
bb44e5d1
IM
225 p->se.exec_start = 0;
226}
227
681f3e68 228#ifdef CONFIG_SMP
e8fa1362
SR
229/* Only try algorithms three times */
230#define RT_MAX_TRIES 3
231
232static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
233static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
234
f65eda4f
SR
235static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
236{
237 if (!task_running(rq, p) &&
73fe6aae
GH
238 (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
239 (p->nr_cpus_allowed > 1))
f65eda4f
SR
240 return 1;
241 return 0;
242}
243
e8fa1362 244/* Return the second highest RT task, NULL otherwise */
79064fbf 245static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
e8fa1362
SR
246{
247 struct rt_prio_array *array = &rq->rt.active;
248 struct task_struct *next;
249 struct list_head *queue;
250 int idx;
251
e8fa1362
SR
252 if (likely(rq->rt.rt_nr_running < 2))
253 return NULL;
254
255 idx = sched_find_first_bit(array->bitmap);
256 if (unlikely(idx >= MAX_RT_PRIO)) {
257 WARN_ON(1); /* rt_nr_running is bad */
258 return NULL;
259 }
260
261 queue = array->queue + idx;
f65eda4f
SR
262 BUG_ON(list_empty(queue));
263
e8fa1362 264 next = list_entry(queue->next, struct task_struct, run_list);
f65eda4f
SR
265 if (unlikely(pick_rt_task(rq, next, cpu)))
266 goto out;
e8fa1362
SR
267
268 if (queue->next->next != queue) {
269 /* same prio task */
79064fbf
IM
270 next = list_entry(queue->next->next, struct task_struct,
271 run_list);
f65eda4f
SR
272 if (pick_rt_task(rq, next, cpu))
273 goto out;
e8fa1362
SR
274 }
275
f65eda4f 276 retry:
e8fa1362
SR
277 /* slower, but more flexible */
278 idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
f65eda4f 279 if (unlikely(idx >= MAX_RT_PRIO))
e8fa1362 280 return NULL;
e8fa1362
SR
281
282 queue = array->queue + idx;
f65eda4f
SR
283 BUG_ON(list_empty(queue));
284
285 list_for_each_entry(next, queue, run_list) {
286 if (pick_rt_task(rq, next, cpu))
287 goto out;
288 }
289
290 goto retry;
e8fa1362 291
f65eda4f 292 out:
e8fa1362
SR
293 return next;
294}
295
296static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
297
6e1254d2 298static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
e8fa1362 299{
6e1254d2 300 int lowest_prio = -1;
610bf056 301 int lowest_cpu = -1;
06f90dbd 302 int count = 0;
610bf056 303 int cpu;
e8fa1362 304
637f5085 305 cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
e8fa1362 306
07b4032c
GH
307 /*
308 * Scan each rq for the lowest prio.
309 */
610bf056 310 for_each_cpu_mask(cpu, *lowest_mask) {
07b4032c 311 struct rq *rq = cpu_rq(cpu);
e8fa1362 312
07b4032c
GH
313 /* We look for lowest RT prio or non-rt CPU */
314 if (rq->rt.highest_prio >= MAX_RT_PRIO) {
610bf056
SR
315 /*
316 * if we already found a low RT queue
317 * and now we found this non-rt queue
318 * clear the mask and set our bit.
319 * Otherwise just return the queue as is
320 * and the count==1 will cause the algorithm
321 * to use the first bit found.
322 */
323 if (lowest_cpu != -1) {
6e1254d2 324 cpus_clear(*lowest_mask);
610bf056
SR
325 cpu_set(rq->cpu, *lowest_mask);
326 }
6e1254d2 327 return 1;
07b4032c
GH
328 }
329
330 /* no locking for now */
6e1254d2
GH
331 if ((rq->rt.highest_prio > task->prio)
332 && (rq->rt.highest_prio >= lowest_prio)) {
333 if (rq->rt.highest_prio > lowest_prio) {
334 /* new low - clear old data */
335 lowest_prio = rq->rt.highest_prio;
610bf056
SR
336 lowest_cpu = cpu;
337 count = 0;
6e1254d2 338 }
06f90dbd 339 count++;
610bf056
SR
340 } else
341 cpu_clear(cpu, *lowest_mask);
342 }
343
344 /*
345 * Clear out all the set bits that represent
346 * runqueues that were of higher prio than
347 * the lowest_prio.
348 */
349 if (lowest_cpu > 0) {
350 /*
351 * Perhaps we could add another cpumask op to
352 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
353 * Then that could be optimized to use memset and such.
354 */
355 for_each_cpu_mask(cpu, *lowest_mask) {
356 if (cpu >= lowest_cpu)
357 break;
358 cpu_clear(cpu, *lowest_mask);
e8fa1362 359 }
07b4032c
GH
360 }
361
06f90dbd 362 return count;
6e1254d2
GH
363}
364
365static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
366{
367 int first;
368
369 /* "this_cpu" is cheaper to preempt than a remote processor */
370 if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
371 return this_cpu;
372
373 first = first_cpu(*mask);
374 if (first != NR_CPUS)
375 return first;
376
377 return -1;
378}
379
380static int find_lowest_rq(struct task_struct *task)
381{
382 struct sched_domain *sd;
383 cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
384 int this_cpu = smp_processor_id();
385 int cpu = task_cpu(task);
06f90dbd
GH
386 int count = find_lowest_cpus(task, lowest_mask);
387
388 if (!count)
389 return -1; /* No targets found */
6e1254d2 390
06f90dbd
GH
391 /*
392 * There is no sense in performing an optimal search if only one
393 * target is found.
394 */
395 if (count == 1)
396 return first_cpu(*lowest_mask);
6e1254d2
GH
397
398 /*
399 * At this point we have built a mask of cpus representing the
400 * lowest priority tasks in the system. Now we want to elect
401 * the best one based on our affinity and topology.
402 *
403 * We prioritize the last cpu that the task executed on since
404 * it is most likely cache-hot in that location.
405 */
406 if (cpu_isset(cpu, *lowest_mask))
407 return cpu;
408
409 /*
410 * Otherwise, we consult the sched_domains span maps to figure
411 * out which cpu is logically closest to our hot cache data.
412 */
413 if (this_cpu == cpu)
414 this_cpu = -1; /* Skip this_cpu opt if the same */
415
416 for_each_domain(cpu, sd) {
417 if (sd->flags & SD_WAKE_AFFINE) {
418 cpumask_t domain_mask;
419 int best_cpu;
420
421 cpus_and(domain_mask, sd->span, *lowest_mask);
422
423 best_cpu = pick_optimal_cpu(this_cpu,
424 &domain_mask);
425 if (best_cpu != -1)
426 return best_cpu;
427 }
428 }
429
430 /*
431 * And finally, if there were no matches within the domains
432 * just give the caller *something* to work with from the compatible
433 * locations.
434 */
435 return pick_optimal_cpu(this_cpu, lowest_mask);
07b4032c
GH
436}
437
438/* Will lock the rq it finds */
4df64c0b 439static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
07b4032c
GH
440{
441 struct rq *lowest_rq = NULL;
07b4032c 442 int tries;
4df64c0b 443 int cpu;
e8fa1362 444
07b4032c
GH
445 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
446 cpu = find_lowest_rq(task);
447
2de0b463 448 if ((cpu == -1) || (cpu == rq->cpu))
e8fa1362
SR
449 break;
450
07b4032c
GH
451 lowest_rq = cpu_rq(cpu);
452
e8fa1362 453 /* if the prio of this runqueue changed, try again */
07b4032c 454 if (double_lock_balance(rq, lowest_rq)) {
e8fa1362
SR
455 /*
456 * We had to unlock the run queue. In
457 * the mean time, task could have
458 * migrated already or had its affinity changed.
459 * Also make sure that it wasn't scheduled on its rq.
460 */
07b4032c 461 if (unlikely(task_rq(task) != rq ||
4df64c0b
IM
462 !cpu_isset(lowest_rq->cpu,
463 task->cpus_allowed) ||
07b4032c 464 task_running(rq, task) ||
e8fa1362 465 !task->se.on_rq)) {
4df64c0b 466
e8fa1362
SR
467 spin_unlock(&lowest_rq->lock);
468 lowest_rq = NULL;
469 break;
470 }
471 }
472
473 /* If this rq is still suitable use it. */
474 if (lowest_rq->rt.highest_prio > task->prio)
475 break;
476
477 /* try again */
478 spin_unlock(&lowest_rq->lock);
479 lowest_rq = NULL;
480 }
481
482 return lowest_rq;
483}
484
485/*
486 * If the current CPU has more than one RT task, see if the non
487 * running task can migrate over to a CPU that is running a task
488 * of lesser priority.
489 */
697f0a48 490static int push_rt_task(struct rq *rq)
e8fa1362
SR
491{
492 struct task_struct *next_task;
493 struct rq *lowest_rq;
494 int ret = 0;
495 int paranoid = RT_MAX_TRIES;
496
a22d7fc1
GH
497 if (!rq->rt.overloaded)
498 return 0;
499
697f0a48 500 next_task = pick_next_highest_task_rt(rq, -1);
e8fa1362
SR
501 if (!next_task)
502 return 0;
503
504 retry:
697f0a48 505 if (unlikely(next_task == rq->curr)) {
f65eda4f 506 WARN_ON(1);
e8fa1362 507 return 0;
f65eda4f 508 }
e8fa1362
SR
509
510 /*
511 * It's possible that the next_task slipped in of
512 * higher priority than current. If that's the case
513 * just reschedule current.
514 */
697f0a48
GH
515 if (unlikely(next_task->prio < rq->curr->prio)) {
516 resched_task(rq->curr);
e8fa1362
SR
517 return 0;
518 }
519
697f0a48 520 /* We might release rq lock */
e8fa1362
SR
521 get_task_struct(next_task);
522
523 /* find_lock_lowest_rq locks the rq if found */
697f0a48 524 lowest_rq = find_lock_lowest_rq(next_task, rq);
e8fa1362
SR
525 if (!lowest_rq) {
526 struct task_struct *task;
527 /*
697f0a48 528 * find lock_lowest_rq releases rq->lock
e8fa1362
SR
529 * so it is possible that next_task has changed.
530 * If it has, then try again.
531 */
697f0a48 532 task = pick_next_highest_task_rt(rq, -1);
e8fa1362
SR
533 if (unlikely(task != next_task) && task && paranoid--) {
534 put_task_struct(next_task);
535 next_task = task;
536 goto retry;
537 }
538 goto out;
539 }
540
697f0a48 541 deactivate_task(rq, next_task, 0);
e8fa1362
SR
542 set_task_cpu(next_task, lowest_rq->cpu);
543 activate_task(lowest_rq, next_task, 0);
544
545 resched_task(lowest_rq->curr);
546
547 spin_unlock(&lowest_rq->lock);
548
549 ret = 1;
550out:
551 put_task_struct(next_task);
552
553 return ret;
554}
555
556/*
557 * TODO: Currently we just use the second highest prio task on
558 * the queue, and stop when it can't migrate (or there's
559 * no more RT tasks). There may be a case where a lower
560 * priority RT task has a different affinity than the
561 * higher RT task. In this case the lower RT task could
562 * possibly be able to migrate where as the higher priority
563 * RT task could not. We currently ignore this issue.
564 * Enhancements are welcome!
565 */
566static void push_rt_tasks(struct rq *rq)
567{
568 /* push_rt_task will return true if it moved an RT */
569 while (push_rt_task(rq))
570 ;
571}
572
f65eda4f
SR
573static int pull_rt_task(struct rq *this_rq)
574{
80bf3171
IM
575 int this_cpu = this_rq->cpu, ret = 0, cpu;
576 struct task_struct *p, *next;
f65eda4f 577 struct rq *src_rq;
f65eda4f 578
637f5085 579 if (likely(!rt_overloaded(this_rq)))
f65eda4f
SR
580 return 0;
581
582 next = pick_next_task_rt(this_rq);
583
637f5085 584 for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
f65eda4f
SR
585 if (this_cpu == cpu)
586 continue;
587
588 src_rq = cpu_rq(cpu);
f65eda4f
SR
589 /*
590 * We can potentially drop this_rq's lock in
591 * double_lock_balance, and another CPU could
592 * steal our next task - hence we must cause
593 * the caller to recalculate the next task
594 * in that case:
595 */
596 if (double_lock_balance(this_rq, src_rq)) {
597 struct task_struct *old_next = next;
80bf3171 598
f65eda4f
SR
599 next = pick_next_task_rt(this_rq);
600 if (next != old_next)
601 ret = 1;
602 }
603
604 /*
605 * Are there still pullable RT tasks?
606 */
607 if (src_rq->rt.rt_nr_running <= 1) {
608 spin_unlock(&src_rq->lock);
609 continue;
610 }
611
f65eda4f
SR
612 p = pick_next_highest_task_rt(src_rq, this_cpu);
613
614 /*
615 * Do we have an RT task that preempts
616 * the to-be-scheduled task?
617 */
618 if (p && (!next || (p->prio < next->prio))) {
619 WARN_ON(p == src_rq->curr);
620 WARN_ON(!p->se.on_rq);
621
622 /*
623 * There's a chance that p is higher in priority
624 * than what's currently running on its cpu.
625 * This is just that p is wakeing up and hasn't
626 * had a chance to schedule. We only pull
627 * p if it is lower in priority than the
628 * current task on the run queue or
629 * this_rq next task is lower in prio than
630 * the current task on that rq.
631 */
632 if (p->prio < src_rq->curr->prio ||
633 (next && next->prio < src_rq->curr->prio))
80bf3171 634 goto out;
f65eda4f
SR
635
636 ret = 1;
637
638 deactivate_task(src_rq, p, 0);
639 set_task_cpu(p, this_cpu);
640 activate_task(this_rq, p, 0);
641 /*
642 * We continue with the search, just in
643 * case there's an even higher prio task
644 * in another runqueue. (low likelyhood
645 * but possible)
80bf3171 646 *
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SR
647 * Update next so that we won't pick a task
648 * on another cpu with a priority lower (or equal)
649 * than the one we just picked.
650 */
651 next = p;
652
653 }
80bf3171 654 out:
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SR
655 spin_unlock(&src_rq->lock);
656 }
657
658 return ret;
659}
660
9a897c5a 661static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
f65eda4f
SR
662{
663 /* Try to pull RT tasks here if we lower this rq's prio */
7f51f298 664 if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
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SR
665 pull_rt_task(rq);
666}
667
9a897c5a 668static void post_schedule_rt(struct rq *rq)
e8fa1362
SR
669{
670 /*
671 * If we have more than one rt_task queued, then
672 * see if we can push the other rt_tasks off to other CPUS.
673 * Note we may release the rq lock, and since
674 * the lock was owned by prev, we need to release it
675 * first via finish_lock_switch and then reaquire it here.
676 */
a22d7fc1 677 if (unlikely(rq->rt.overloaded)) {
e8fa1362
SR
678 spin_lock_irq(&rq->lock);
679 push_rt_tasks(rq);
680 spin_unlock_irq(&rq->lock);
681 }
682}
683
4642dafd 684
9a897c5a 685static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
4642dafd 686{
9a897c5a 687 if (!task_running(rq, p) &&
a22d7fc1
GH
688 (p->prio >= rq->rt.highest_prio) &&
689 rq->rt.overloaded)
4642dafd
SR
690 push_rt_tasks(rq);
691}
692
43010659 693static unsigned long
bb44e5d1 694load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
e1d1484f
PW
695 unsigned long max_load_move,
696 struct sched_domain *sd, enum cpu_idle_type idle,
697 int *all_pinned, int *this_best_prio)
bb44e5d1 698{
c7a1e46a
SR
699 /* don't touch RT tasks */
700 return 0;
e1d1484f
PW
701}
702
703static int
704move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
705 struct sched_domain *sd, enum cpu_idle_type idle)
706{
c7a1e46a
SR
707 /* don't touch RT tasks */
708 return 0;
bb44e5d1 709}
deeeccd4 710
73fe6aae
GH
711static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
712{
713 int weight = cpus_weight(*new_mask);
714
715 BUG_ON(!rt_task(p));
716
717 /*
718 * Update the migration status of the RQ if we have an RT task
719 * which is running AND changing its weight value.
720 */
721 if (p->se.on_rq && (weight != p->nr_cpus_allowed)) {
722 struct rq *rq = task_rq(p);
723
deeeccd4 724 if ((p->nr_cpus_allowed <= 1) && (weight > 1)) {
73fe6aae 725 rq->rt.rt_nr_migratory++;
deeeccd4 726 } else if ((p->nr_cpus_allowed > 1) && (weight <= 1)) {
73fe6aae
GH
727 BUG_ON(!rq->rt.rt_nr_migratory);
728 rq->rt.rt_nr_migratory--;
729 }
730
731 update_rt_migration(rq);
732 }
733
734 p->cpus_allowed = *new_mask;
735 p->nr_cpus_allowed = weight;
736}
deeeccd4 737
bdd7c81b
IM
738/* Assumes rq->lock is held */
739static void join_domain_rt(struct rq *rq)
740{
741 if (rq->rt.overloaded)
742 rt_set_overload(rq);
743}
744
745/* Assumes rq->lock is held */
746static void leave_domain_rt(struct rq *rq)
747{
748 if (rq->rt.overloaded)
749 rt_clear_overload(rq);
750}
cb469845
SR
751
752/*
753 * When switch from the rt queue, we bring ourselves to a position
754 * that we might want to pull RT tasks from other runqueues.
755 */
756static void switched_from_rt(struct rq *rq, struct task_struct *p,
757 int running)
758{
759 /*
760 * If there are other RT tasks then we will reschedule
761 * and the scheduling of the other RT tasks will handle
762 * the balancing. But if we are the last RT task
763 * we may need to handle the pulling of RT tasks
764 * now.
765 */
766 if (!rq->rt.rt_nr_running)
767 pull_rt_task(rq);
768}
769#endif /* CONFIG_SMP */
770
771/*
772 * When switching a task to RT, we may overload the runqueue
773 * with RT tasks. In this case we try to push them off to
774 * other runqueues.
775 */
776static void switched_to_rt(struct rq *rq, struct task_struct *p,
777 int running)
778{
779 int check_resched = 1;
780
781 /*
782 * If we are already running, then there's nothing
783 * that needs to be done. But if we are not running
784 * we may need to preempt the current running task.
785 * If that current running task is also an RT task
786 * then see if we can move to another run queue.
787 */
788 if (!running) {
789#ifdef CONFIG_SMP
790 if (rq->rt.overloaded && push_rt_task(rq) &&
791 /* Don't resched if we changed runqueues */
792 rq != task_rq(p))
793 check_resched = 0;
794#endif /* CONFIG_SMP */
795 if (check_resched && p->prio < rq->curr->prio)
796 resched_task(rq->curr);
797 }
798}
799
800/*
801 * Priority of the task has changed. This may cause
802 * us to initiate a push or pull.
803 */
804static void prio_changed_rt(struct rq *rq, struct task_struct *p,
805 int oldprio, int running)
806{
807 if (running) {
808#ifdef CONFIG_SMP
809 /*
810 * If our priority decreases while running, we
811 * may need to pull tasks to this runqueue.
812 */
813 if (oldprio < p->prio)
814 pull_rt_task(rq);
815 /*
816 * If there's a higher priority task waiting to run
817 * then reschedule.
818 */
819 if (p->prio > rq->rt.highest_prio)
820 resched_task(p);
821#else
822 /* For UP simply resched on drop of prio */
823 if (oldprio < p->prio)
824 resched_task(p);
e8fa1362 825#endif /* CONFIG_SMP */
cb469845
SR
826 } else {
827 /*
828 * This task is not running, but if it is
829 * greater than the current running task
830 * then reschedule.
831 */
832 if (p->prio < rq->curr->prio)
833 resched_task(rq->curr);
834 }
835}
836
bb44e5d1
IM
837
838static void task_tick_rt(struct rq *rq, struct task_struct *p)
839{
67e2be02
PZ
840 update_curr_rt(rq);
841
bb44e5d1
IM
842 /*
843 * RR tasks need a special form of timeslice management.
844 * FIFO tasks have no timeslices.
845 */
846 if (p->policy != SCHED_RR)
847 return;
848
849 if (--p->time_slice)
850 return;
851
a4ec24b4 852 p->time_slice = DEF_TIMESLICE;
bb44e5d1 853
98fbc798
DA
854 /*
855 * Requeue to the end of queue if we are not the only element
856 * on the queue:
857 */
858 if (p->run_list.prev != p->run_list.next) {
859 requeue_task_rt(rq, p);
860 set_tsk_need_resched(p);
861 }
bb44e5d1
IM
862}
863
83b699ed
SV
864static void set_curr_task_rt(struct rq *rq)
865{
866 struct task_struct *p = rq->curr;
867
868 p->se.exec_start = rq->clock;
869}
870
5522d5d5
IM
871const struct sched_class rt_sched_class = {
872 .next = &fair_sched_class,
bb44e5d1
IM
873 .enqueue_task = enqueue_task_rt,
874 .dequeue_task = dequeue_task_rt,
875 .yield_task = yield_task_rt,
e7693a36
GH
876#ifdef CONFIG_SMP
877 .select_task_rq = select_task_rq_rt,
878#endif /* CONFIG_SMP */
bb44e5d1
IM
879
880 .check_preempt_curr = check_preempt_curr_rt,
881
882 .pick_next_task = pick_next_task_rt,
883 .put_prev_task = put_prev_task_rt,
884
681f3e68 885#ifdef CONFIG_SMP
bb44e5d1 886 .load_balance = load_balance_rt,
e1d1484f 887 .move_one_task = move_one_task_rt,
73fe6aae 888 .set_cpus_allowed = set_cpus_allowed_rt,
bdd7c81b
IM
889 .join_domain = join_domain_rt,
890 .leave_domain = leave_domain_rt,
9a897c5a
SR
891 .pre_schedule = pre_schedule_rt,
892 .post_schedule = post_schedule_rt,
893 .task_wake_up = task_wake_up_rt,
cb469845 894 .switched_from = switched_from_rt,
681f3e68 895#endif
bb44e5d1 896
83b699ed 897 .set_curr_task = set_curr_task_rt,
bb44e5d1 898 .task_tick = task_tick_rt,
cb469845
SR
899
900 .prio_changed = prio_changed_rt,
901 .switched_to = switched_to_rt,
bb44e5d1 902};